Mark a backend as sick using VCL

sick_backend.vtc

varnishtest "Temporary sick backends"

server s1 {
	rxreq
	txresp
	rxreq
	txresp
} -start

varnish v1 -vcl+backend {
	import directors;
	import kvstore;

	sub vcl_init {
		# Use kvstore 0 for sick backends
		kvstore.init(0, 25000);

		new sick = directors.round_robin();
	}

	sub vcl_recv {
		# Set Host as sick for 2s
		if (req.method == "SICK") {
			kvstore.set(0, req.http.Host, "sick", 2s);
			return (synth(200));
		}

		# Is backend flagged as sick?
		if (kvstore.get(0, req.http.Host, "") == "sick") {
			set req.backend_hint = sick.backend();
		}

		return (pass);
	}
} -start

client c1 {
	txreq -hdr "Host: abc"
	rxresp
	expect resp.status == 200

	txreq -req SICK -hdr "Host: abc"
	rxresp

	txreq -hdr "Host: abc"
	rxresp
	expect resp.status == 503

	delay 3

	txreq -hdr "Host: abc"
	rxresp
	expect resp.status == 200
} -run